A convicted murderer flashed a loaded gun during an argument Wednesday on a Bronx subway train — and was arrested nearby with the weapon, police sources said.

Lavalle Johnson, 46, who lives on Manhattan’s Upper East Side, was charged with two felony weapon offenses and a violation of local law.

Police in Transit District 11 responded to reports of a heated argument on the northbound 2 train at the 149th Street/Grand Concourse station at 8:23 a.m. A man reportedly displayed a gun and fled, sources said.

Sources say Johnson served 20 years for a May 31, 1993 homicide on E. 226th St. in the Bronx. He was convicted of murdering one person and attempted murder of another who he shot in the leg. He was paroled in 2013.